In general, the invention relates to idle speed control of an internal combustion engine. More specifically, the invention relates to a method and system for alternator load modeling that provides stability within a dynamic electrical generation system during idle operations.
Internal combustion engines include, among many others, systems for controlling idle speed. Such control impacts many aspects of vehicle operation including fuel efficiency, engine functionality, and the like. For example, fuel efficiency may be maximized when a vehicle operates with a lower idle speed. However, engine functionality may be impaired if idle speed reaches too low of a value due to unavailable torque. Additionally, the lower the engine idle speed, the greater the impact various loadings have on the engine.
A dynamic electrical generation system, also referred to as an alternator, frequently exerts variable loading based on electrical generation power requirements. For example, a mobile vehicle operator may engage power windows, rear defogger, multiple A/C blower settings, cooling fan, and the like. All represent an additional load on the internal combustion engine and the concomitant variations in idle speed. In the past, such challenges have been met with ideas such as setting idle speed to a value that would sustain an acceptable level under maximum loading conditions. Another strategy is to modify the engine air rate in response to the engine speed variations. Unfortunately, either solution results in excessive engine speed fluctuation as electrical loading is applied and removed from the system.
It would be desirable, therefore, to provide a method and system that would overcome these and other disadvantages.
The present invention is directed to a system and method for controlling idle speed for an internal combustion engine. The invention provides voltage generator load modeling that anticipates load changes and provides stability within a dynamic electrical generation system during idle operations.
One aspect of the invention provides a method for controlling idle speed for an internal combustion engine by monitoring a plurality of vehicle system signal inputs, determining a baseline load control signal based on the vehicle system signal inputs, determining a maximum load control signal based on the vehicle system signal inputs, determining an anticipated load control signal based on the vehicle system signal inputs, determining an idle speed control signal based on the baseline control signal and the anticipated control signal, modifying the idle speed control signal based on vehicle system signal inputs, and controlling the idle speed based on the modified idle speed control signal.
In accordance with another aspect of the invention, a system for controlling idle speed for an internal combustion engine is provided. The system includes means for monitoring a plurality of vehicle system signal inputs. The system further includes means for means for determining a baseline load control signal based on the vehicle system signal inputs. Means for determining a maximum load control signal based on the vehicle system signal inputs is provided. Means for determining an anticipated load control signal based on the vehicle system signal inputs is also provided. The system further includes means for determining an idle speed control signal based on the baseline control signal and the anticipated control signal. The system additionally includes means for modifying the idle speed control signal based on vehicle system signal inputs and means for controlling the idle speed based on the modified idle speed control signal.
In accordance with yet another aspect of the invention, a computer readable medium storing a computer program includes: computer readable code for receiving a plurality of vehicle system signal inputs; computer readable code for determining a baseline load control signal based on the vehicle system signal inputs; computer readable code for determining a maximum load control signal based on the vehicle system signal inputs; computer readable code for determining an anticipated load control signal based on the vehicle system signal inputs; computer readable code for determining an idle speed control signal based on the baseline control signal and the anticipated control signal; computer readable code for modifying the idle speed control signal based on vehicle system signal inputs; and computer readable code for controlling the idle speed based on the modified idle speed control signal.